How do I properly defrost/refreeze saved seed?

[Cate]

This is my first post.

I have a freezer full of heirloom seeds I've collected over the years, most from seed companies, some I saved myself. I recently learned that because they might not have been dry enough, even coming from the seed companies, that they might have been damaged by freezing. So I'd like to take out my entire stock and check viability. They are mostly stored in their original packets inside canning jars. Some of the jars had the air removed with a Pump-N-Seal, others didn't. None of the seeds in the freezer have been defrosted prior to now.

If I defrost them, I know I have to let the jars come up to room temp and stop sweating before opening the jars. My plan is to germinate a few seeds from each packet, then dry the remaining seeds further, reseal their containers and refreeze them. I also want to make an inventory list so that I can find them and quickly remove them from the freezer when I want to plant.

So here are my questions:

a.) Does anyone have experience with defrosting and refreezing seeds and how that has affected later germination rates? I read on one website that repeated freezing and defrosting can damage seeds, but I don't know how much damage I'd cause by just doing it once.

b.) Will I cause any damage to the seeds if I further dry them now (I'm using a food dehydrator) and then refreeze them? (As opposed to superdrying them prior to freezing them the first time.) Or if they germinate, should I just leave them at their current level of dryness and refreeze them?

I appreciate any help the members can offer. Thanks in advance.

Cate

[Cate]

Anyone have any ideas?
Cate

[Dreyadin]

Not a SSE member except in the forum for now... but I may be able to explain a little bit for you.

Seeds have a phase called the glass stage. Each variety/ species is a bit different from the next. The glass stage is where a seed is essentially frozen in time. That dormancy is impacted by both moisture and temperature. Maintaining the dormancy is the goal for extended seed storage as that effects viability. Once the glass stage is broken... it is broken. There is no putting the seed back into this suspended again as it has begun hormone and enzyme changes already. It is essentially awakened and now living off of it's energy reserves. This is why constant, meticulous attention is needed in seed vaults.

While many seeds are capable of remaining dormant for years and still retain viability in just cool temperatures after being properly dried... long term storage (by long term I mean for many years) is maintained by freezing.

Water, when frozen, makes sharp crystals that can rupture cells. As well moisture is needed for microbes to proceed with decomposition. The seeds undergo a series of enzyme and hormone changes during drying that prepares the seed for the wait until proper conditions for germination. That's the cliff notes as to why seeds are dried.

You really do not want to freeze and refreeze seeds if at all possible because it is the temperature fluctuations you are actually wanting to avoid.

Pack seeds into portions you intend on using for a year (plus a few extras.. just in case) in separate containers. This way you minimize the exposure of the seeds that are to remain in storage.

How dry the seeds need to be for storage in freezing temperatures is in direct relation to how cold the storage temperatures will be. Somehow, I doubt you'll be hitting the subzero ranges the seed vaults utilize which then requires moisture content to be at 8% and less.

While a freeze session is useful for many seed crops that have issues with seed weevils, many seeds will hold for quite a few years without the artic exposure.

Quality of the seed plays a big part in the storage, and in particular what species you are saving. Seeds sold on the market need only to pass their germination testing percentages before getting a "sell by" date that is valid for over a year from the time of the test. This is not a major issue if you are planting them out that year.. it can be an issue if you are looking to store them, especially long term.

The issue with a dehydrator is heat. Some produce heat even on the fan only mode. I've had more than a few friends essentially roast their seeds only to discover the following year their predicament. Desiccants are an option should you be in a high humidity area that inhibits air drying naturally.

What crops are you looking to save, and for how long?

[Cate]

Thanks, Dreyadin, for your advice. The seeds that I currently have in the freezer are all types. Some are seeds I purchased from seed companies, and placed in jars, then froze. Some are seeds I saved myself.

But I did not (as you advised) pack them in 1 year supplies. I also am not sure if they were dry enough when I froze them, so I don't know if they're all dead now and need replaced. That's why I want to test germination and then store them again in the freezer in, as you suggest, 1-year groups.

As for drying seeds with my dehydrator, I have practiced this and I've got it down pretty good. My dehydrated seeds have germinated fine.

So are you saying that it's impossible to remove the seeds from the freezer, bring them up to room temp, and then successfully re-freeze them? Because once they come to room temp, they've broken the glass stage and can never return to it? So re-freezing them would definitely kill them? I think this is what you're saying, am I correct?

If so, what is the maximum time I can have them out of the freezer for inventoring the stock without harming them? A minute? 5 minutes? If absolutely necessary, I can stand in the open door of the freezer and just do one jar at a time and then shut the door, then do one more jar later, etc, but then is that going to warm up everything in the freezer so much as to harm all the seeds in it? Or is it more important to keep the door closed, and just grab one jar, take it to the kitchen, and try to inventory my stock while peaking through the closed jar? (There are several packets in each jar. Unfortunately they're various veggie packets.)

Cate

[Dreyadin]

The fluctuation begins the deterioration of the seed's viability. In other words, it starts the clock ticking on the storage life when you subject it to temperature swings. In testing some of the studies used 40 degree temperature fluctuations.

If you are curious.. here is an interesting thing to read. That link goes a bit into detail about it. The search to figure out why some seeds can remain viable for hundreds of years (oldest seed ever germinated so far was a 2,000 year old Judean palm seed.. they named the palm Methuselah), while others can not, is still a work in progress.

Dividing your stored seeds is mainly an insurance policy. Especially when you feel the need to rifle through your seeds, packing them in yearly allotments means you can still enjoy doing that without effecting the stash entirely.

I guess what I am trying to get at is... what is YOUR definition of long term storage?

Many will hold quite a few years in a jar in the basement. Like tomatoes, peppers, spinach, squash, melons, basil, dill, tomatillos, parsley, gourds, mustard greens, swiss chard, broccoli... those are just some I have grown from seed that I had packed away (read... lost and rediscovered) for over 10 years.

[punkinhead]

I have had seeds stored for over 15 years now. For many years they were just stored in a closet in the house. For about the last 8 years they have been in an old freezer in dad's shop. The freezer has never been turned on but the insulation in it keeps the seeds from enduring the extreme temperature changes between day/night and winter/summer. I planted banana squash seed from there last year that I had purchased in 1994. They seemed to grow as well as when the seed was new. I keep the seeds in glass jars with tight lids or big popcorn tins like the ones you see around Cristmas time. My luck with peas stored in the same way was disappointing.

Punkinhead

[Cate]

Originally posted by Dreyadin:

The fluctuation begins the deterioration of the seed's viability. In other words, it starts the clock ticking on the storage life when you subject it to temperature swings.

I guess what I am trying to get at is... what is YOUR definition of long term storage?

So - bottom line - if I defrost my seeds, I cannot refreeze them and expect them to remain viable for, say, five years, correct? (This is the question I'm trying to get a definitive answer for.)

[spacecase0]

I have been storing my seeds in the freezer for a while now,
and I take jars out to get more seeds, let them warm up to room temp, and then refreeze and that does not seem to hurt the storage life, but then I have only frozen and thawed out seeds about 5 times over a period of many years, at least so far that I have tested,
humidity cycling really seems to hurt seeds, if you wake them up with higher humidity, you will hurt them badly trying to put them back to sleep.
and daily tempreature changes also seem to hurt if it lasts for any length of time
I also do not store my seeds in an oxygen environment, so maybe that changes something... I also plant them immediately when I take them out (or I repack in another canning jar without air) because some of mine are stored over dry (because they were dry frozen), and they can't take oxygen in the air without getting hurt
I also don't leave the seed jars open long at all, just enough to take out the ones I am planting, and I often defrost them in a freezer bag so it takes a few days for them to warm up.

here is a wonderful web page by someone that studied long term seed storage his entire life
http://www.seedcontainers.net/a_guid...servation.html

edit:
also check this out
http://www.savingourseeds.org/resources.html